Subject: spufs: fix possible memory corruption is spufs_mem_write From: Arnd Bergmann Due to a buggy unsigned comparison, it was possible to write beyond the end of the local store file in spufs under some circumstances. This rewrites the buggy function to look more like simple_copy_from_buffer. Signed-off-by: Arnd Bergmann Cc: Ulrich Weigand Index: linux-2.6/arch/powerpc/platforms/cell/spufs/file.c =================================================================== --- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/file.c +++ linux-2.6/arch/powerpc/platforms/cell/spufs/file.c @@ -64,8 +64,8 @@ static ssize_t spufs_mem_read(struct file *file, char __user *buffer, size_t size, loff_t *pos) { - int ret; struct spu_context *ctx = file->private_data; + ssize_t ret; spu_acquire(ctx); ret = __spufs_mem_read(ctx, buffer, size, pos); @@ -75,25 +75,29 @@ spufs_mem_read(struct file *file, char _ static ssize_t spufs_mem_write(struct file *file, const char __user *buffer, - size_t size, loff_t *pos) + size_t size, loff_t *ppos) { struct spu_context *ctx = file->private_data; char *local_store; + loff_t pos = *ppos; int ret; - size = min_t(ssize_t, LS_SIZE - *pos, size); - if (size <= 0) + if (pos < 0) + return -EINVAL; + if (pos > LS_SIZE) return -EFBIG; - *pos += size; + if (size > LS_SIZE - pos) + size = LS_SIZE - pos; spu_acquire(ctx); - local_store = ctx->ops->get_ls(ctx); - ret = copy_from_user(local_store + *pos - size, - buffer, size) ? -EFAULT : size; - + ret = copy_from_user(local_store + pos, buffer, size); spu_release(ctx); - return ret; + + if (ret) + return -EFAULT; + *ppos = pos + size; + return size; } static unsigned long spufs_mem_mmap_nopfn(struct vm_area_struct *vma,